1. Field of the Invention
This invention relates to a bed for a machine tool, wherein the bed has a fluid channel.
2. Discussion of the background
Metal working by a machine tool conventionally requires fluid, for example a coolant in order to cool down a contact point between a workpiece and the machining tool, oil in order to lubricate or cool down the machining tool, etc. The fluid is collected and resupplied by a circulatory conduit.
A conventional machine tool 1 is shown in a perspective view in FIG. 1, in a side view FIG. 2(A) and in a front view in FIG. 2(B). The upper surface of a bed 10 of the machine tool 1 has a recess that forms a fluid channel 16 where fluid flows. For example, the fluid is a coolant for cooling down a contact point between the machining tool (not shown) mounted on a tool spindle stock 20 and a workpiece (not shown) supported by a head stock 14 and a tail stock 15. The fluid is supplied to the contact point between the machining tool and the workpiece, drops into the fluid channel 16, is collected to a tank (not shown) and is resupplied to the contact point.
It is preferable that the rigidity of the bed 10 is high. The reason is that deformation of the bed results from low rigidity so as to cause an error of the relative position between the workpiece and the machining tool, even if the machining tool on the tool spindle stock 20 is accurately controlled.
However the presence of the fluid channel 16 lowers the rigidity of the bed 10. That causes rotational vibration of the head stock 14, the tail stock 15, the table 15a, etc. around the X-axis, as shown in FIG. 2(A). Thus there may occur fluctuation of the relative position between the workpiece and the machining tool so that the machining accuracy may be lower. Additionally, as shown in FIG. 2(B), because of recent requirements of downsizing, some machine tools 1 have the head stock 14, etc. overhanging the side 10L of the bed 10. In such machine tool 1, the rotational vibration of the head stock 14, etc. around Z-axis may be increased because of the low rigidity of the bed 10, so that the machining accuracy may be lower.